"Mum will meet Sherlock," exec producer Rob Doherty told TVLine. "Given what we know about mum - or heard about mum - and given what we know for sure about Sherlock, you can see it going a certain way. I feel like we're going to tell a story with a few lovely, little surprises."

Watson's mother will appear in the CBS drama's ninth episode, currently scheduled to air on December 13 in the US.

Foh Shen has previously played recurring roles on ABC medical series Gideon's Crossing, family drama Everwood and CBS crime procedural Close to Home, with guest stints on the likes of 24, Desperate Housewives and Boston Legal.